The present invention relates to a valve for opening and closing the communication between a first and a second conduit, the valve comprising a housing with an upper portion, a lower portion and an interposed communication which may be closed and opened by means of two spaced apart sealing members which each cooperate with their obstruction members for forming double seals between the upper and lower portions of the housing, which portions may be connected each to a conduit.
Valves of the cone type which form double obstructions between two conduits are well known. When these valves are closed, there is formed between the two obstructions a space which is in communication with the atmosphere. The advantage inherent in these valves is that leakage in one of the obstructions is led out into the atmosphere outside the valve. This arrangement prevents liquid from the one conduit from being mixed with liquid in the other conduit interconnected to the valve.
In processing plants it is desirable to be able to shut off various sections of an installation from each other in a reliable manner so as to prevent mixture of different media. For example, it is occasionally desirable to shut off a section of the installation for cleaning purposes, while the remaining parts of the installation are in operation and are filled with processing medium. In such cases, it is necessary to ensure that cleaning liquid from that section which is being cleaned cannot leak into the processing medium in the section of the installation which is still in operation. In order to satisfy this requirement, use is normally made of double valves or valves with double cones of the type described in West German Pat. No. DT 26 32 587, the disclosure of which is hereby incorporated by reference.
Valves used hitherto for this purpose have, however, proved to possess a plurality of inconveniences. Thus, a minor amount of liquid often leaks out when the valve is switched, either because the interior of the valve is momentarily placed in communication with the bleeder outlet or because a body of liquid enclosed between the two sealing surfaces leaks out through the same outlet. The above inconvenience entails that cleaning of the bleeder chamber and its outlet must often be carried out. When the double reliability of the valve is deranged on flushing with cleaning liquid through the bleeder chamber, this is a serious shortcoming in the valve.
It would, therefore, be desirable if the intervals between such cleaning operations could be extended such that cleaning is effected at times when no product is present in the conduits.
There is a known possibility of circumventing these difficulties, namely with a valve of the sliding type in which the shut off member consists of a movable ported cylinder. However, this valve is based on a constructional principle which has proved in practice to possess diadvantages in the form of heavy wear on the sealing members and movable fittings. Neither is this principle applicable to conventional valves of the cone type, which entails that the principle cannot be utilized for reconstructing extant, conventional cone valves. Furthermore, the lower chamber of the valve contains a pocket constituting the communication with the upper chamber of the valve, this pocket being unsuitable from the point of view of cleaning operations.